I already have multiple copies of my wallet. But a new user would not know how to do this. Streamlining it by including it as an automatic option in the client would make the learning curve for bitcoin much shallower, and much less dangerous to your coins.
And I'm rereading about the deterministic wallets in clients like Armory. I still like the simplicity of my idea more though.
What is a simpler backup solution than printing/copying your wallet once and never having to back it up again? And the paper backup is even better than USB keys or servers, because you never have to worry about the USB key working when you plug it in a year from now, or a HDD/server failing. Plus, a sheet of paper is a LOT cheaper and a lot easier to hide, and its integrity is visually verifiable.
Not to mention you can still backup the encrypted version to a server somewhere, but I don't see the necessity of risking something like the 0.4.0 wallet-not-actually